Trapezius Strength Balance

Hello community, I had a question regarding trapezius strength. I know this isn't a weightlifting forum but the exercises are quite similar, what is the goal or ideal percentage of bodyweight for prone overhead trap raises? Is there a ratio to trap shrugs or handstand shrugs?  Or is there another movement  is must be balanced with in a certain ratio to have balanced trapezius strength? Is there a ratio to shoulder strength?

Or can anyone point me to a resource that could answer my question?

.A normal person who can show easily and I mean EASILy the wall slide has healthy and balanced shoulders

if this represents an answer for you is fine. if not I do not have the answer for you. since the question is not really specific for any type of sport there is no reason to make a scientific research for it.

Well in general, the lower trapezius is a muscle that tends to be under emphasized. It's important for many upper body movements, posture, etc. If we want to improve its strength, some here would say press handstands or planche, etc. would do so. For assistance work or mobility work, where we want to have the strength to bring our arms overhead under load something like overhead raises would be a nice addition for more targeted work. What should our aim be in this movement, simply activation or reach a certain load? I ask for its carryover to gymnastics upper body strength as well as various lifts. 

Correct activation over the time with a full range of motion, this means for the wall slide set long up to 4-6 minutes in a row.